Prone testing does not assume that minimal femoral motion will occur as there is nothing to act as a stabilizer to the thigh.

The subject is prone and the thigh support extends to allow the knee to be off the edge of the seat. The seat can be seen as the red line whilst the blue stars represent the joint line.

Stabilization is normally accomplished using femoral and pelvic strapping and the subject is allowed to hold the chair or the handles provided.